18. rnai is a technique that silences genes by targeting them and degrading their mrna. how can this technique be used in scientific laboratories? a. rnai is observed in nature, but it can't be used in laboratories. b. rnai allows scientists to turn off one gene specifically to study its effect. c. rnai has been used in laboratories to make bacteria more susceptible to antibiotics, but has limited application in eukaryotic cells. d. rnai is a powerful tool for degrading mrna, but because it doesn't degrade other types of rna, its use is limited.

(select all the correct choose each statement that is scientific. - the opinions of randomly selected participants in a survey prove the idea that global temperatures are not increasing on earth. - the universe's average temperature and rate of expansion support the idea that it began as one super-dense and hot mass 13.8 billion years ago. - ocean tides are caused by the uneven gravitational pulls of the moon and sun on different parts of earth. - human life is more valuable than other forms of life on earth because humans are more intelligent than other organisms.